Answered by Ustadh Tabraze Azam
Question: Assalamualeykum waramatulahi wabarakatu Ya Sheik, I kiss my girl friends in my dreams and I feel a little moisture on my private parts. Can I offer prayers without taking a bath or by only washing my private parts?
Answer: Wa alaikum assalam wa rahmatullahi wa barakatuh,
I pray that you are in the best of health and faith, insha’Allah.
Pre-sexual fluid (madhi) invalidates your ablution, yet does not necessitate the ritual bath (ghusl).
In general, less than 5cm in diameter of liquid filth is excused, though it is superior to clean yourself before praying.
Please see: Please List All the Nullifiers of Ablution According to the Hanafi School and: Regarding Ghusl and Wet Dreams for Men and Women
And Allah alone gives success.